Anisocytosis or mixed anemia: This condition is characterized by a mixture of microcytic and macrocytic anemia, which could lead to a decrease in MCV (Mean Corpuscular Volume) and MCH (Mean Corpuscular Hemoglobin) with a decrease in hemoglobin and hematocrit. Normal ferritin and iron levels suggest that iron deficiency is not the primary cause, but the mixed picture could be due to various factors including chronic disease, vitamin deficiencies, or other underlying conditions.

Chronic Disease Anemia: Conditions like chronic kidney disease, rheumatoid arthritis, or chronic infections can lead to a decrease in hemoglobin and hematocrit due to inflammation and cytokine release affecting erythropoiesis. Normal ferritin and iron levels are consistent with this diagnosis, as the issue is not with iron availability but with its utilization.
Thalassemia Trait: This genetic disorder can cause microcytic anemia (low MCV) with a decrease in hemoglobin and hematocrit. Ferritin and iron levels can be normal, as the problem lies in the production of the hemoglobin chains, not in iron availability.
Sideroblastic Anemia: Although less common, this condition involves a defect in heme synthesis, leading to increased iron storage within mitochondria of red blood cell precursors. It can present with microcytic anemia and normal or elevated ferritin and iron levels.

Myelodysplastic Syndrome (MDS): A group of disorders caused by poorly formed or dysfunctional blood cells, MDS can lead to a decrease in hemoglobin, hematocrit, MCV, and MCH. Normal ferritin and iron levels do not rule out MDS, as the issue is with the bone marrow's ability to produce healthy blood cells.
Bone Marrow Failure Syndromes: Conditions like aplastic anemia or pure red cell aplasia can cause a decrease in blood cell production, leading to low hemoglobin and hematocrit. These are critical to diagnose early due to their potential for severe complications and the need for specific treatments.

Copper Deficiency: Although rare, copper deficiency can cause microcytic anemia with decreased hemoglobin and hematocrit. Normal ferritin and iron levels would not be inconsistent with this diagnosis, as copper plays a role in hemoglobin synthesis and iron metabolism.
Vitamin Deficiencies (e.g., Vitamin B6): Certain vitamin deficiencies can affect hemoglobin synthesis and lead to anemia. While less common, they should be considered, especially if other causes have been ruled out and there's a suggestive dietary or clinical history.